Directional aerial



De@ 19, 195o T. KAHAN Em. 2,534,451

DIRECTIONAL AERIAL Filed May 26, 1947 2 Sheets-Sheet 1 INVENTURS THEO. KAHAN BYALBERT WACLHE' De. 19, 1950 lT. KAHA'N ETAL 2,534,451

DIRECTIONAL AERIAL -Filed May 26. 194'? 2 Sheets-Sheet 2 INVENTR THEO KAHAN ByALBERTk/AC-HE Patented Dec. 19, 17.950

DIRECTIONAL AERIAL Tho Kahan and Albert Wach, Paris, France, assignors to Radio Industrie S. A., Paris, France, a society of France Application May 26, 1947, Serial No. 750,408

Y In France May 31, 1946 (Cl. Z50-33.63)

3 Claims.

Our invention relates to scanning directional aerials for very short electromagnetic waves.

The object of our invention is to provide an aerial of this type which is better adapted to meet the requirements of practice than those used for the same purpose up to the present time.

Preferred embodiments of our invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example and in which:

Fig. 1 is a general View of the mirror included in an aerial according` to our invention;

Fig. 2 is a diagrammatic perspective view of a wave guide and the system of slotted screen associated therewith according to our invention, the wave guide being shown raised above the position it normally occupies with respect to the slotted screen;

Fig. 3 is a diagrammatic perspective View of a slotted screen to -be used in connection with our invention;

Fig. 4 is a diagrammatic perspective view of a reciprocating slotted wave guide for use in connection with our invention;

Fig. 5 shows a modication of the device of Fig. 4;

Fig. 6 is a diagrammatic sectional view of a portion of a Wave guide provided with wave radiating elements;

Fig. '7 shows a modification of the device of Fig. 6:

Figs. 8a and 8b are explanatory diagrams.

The aerial according to our invention includes a reflecting mirror I (Fig. l), a wave guide 2 adapted to emit at least one electromagnetic Wave beam, suitably located with respect to this mirror, and means for periodically modifying the wave beam issuing from said Wave guide toward said mirror so as to obtain a directional wave beam of substantially plane shape which scans a given dihedral angle of space.

The mirror shown by Fig. 1 has its surface generated by a parabola P1 which remains always parallel to a given plane and is displaced so that its vertex is always located on another parabola P2 xed in space and the plane of which is at right angle to every parabola P1, parabola P2 and the parabola P1 that passes through the vertex thereof having coinciding axes, along what will be called the axis of the mirror. The focal length of P2 is greater than that of P1.

A wave guide is adapted to transmit electromagnetic waves to be reiiected by mirror l. Therefore this wave guide has an open lateral face turned towards this mirror and it is located in such manner that its axis is at right angle to the plane of parabola P2 and intersects the axis of mirror I at the focus of the parabola P1 that passes through the vertex of Pz. This wave guide is supplied with high frequency electromagnetic waves through any suitable means not shown on the drawing.

Means are interposed between said wave guide and said mirror so as to control the distribution of the electromagnetic flux issuing from said wave guide so as to obtain, after reflection on the mirror, a fiat beam which scans a desired angle of space.

Said means may be `constituted by a screen adapted to stop electromagnetic waves and provided with suitably disposed slots.

In the embodiment of Figs. 2 and 3, said screen is independent of the wave guide and is movable with respect thereto. In the modication of Fig. 2, the screen is constituted by a continuous strip 3 of nietallized rubber passing around drums 3a and driven with a continuous movement, `for instance by one of said drums. The two parallel portions of said strip run on either side of wave guide 2 (which, in Fig. 2 is shown above its actual level for the sake of clarity but is in fact located at the level .of drums 3.a) Thus the slots pro vided in strip 3 travel :along the .open face .ci wai/,e guide 2 between said guide and mirror l toward which this open face is turned, The slots provided in strip 3 are so dimensioned and spaced with respect to one another that the wave beams passing through said slots are reflected from the mirror in the form of scanning fiat beams turning always in the same direction about an axis at right angles to the wave guide, each beam that reaches the end of its scanning angie being replaced by a new beam starting from the other end of said angle.

In the embodiment of Fig. 3, the screen is constituted by a plate 4 carried on sliding rod 5 operated by cams G (such as rregold cams) which impart a reciprocating sliding movement to said screen. With this arrangement, scanning takes place alternately in one direction and in the opposed one.

In the embodiment of Fig. 4, the screen is constituted by the face of the Wave guide that is turned toward the mirror, this face being provided with suitable slots for the passage of electromagnetic wave beams. In this case a reciprocating sliding movement is imparted to wave guide 2 by a cam l acting on a push rod rigid with said guide. A spring 8 urges said guide in the opposed direction.

In the modification of Fig. 5, the movement of guide 2 is imparted thereto by means of cranks S. Thus guide 2 is given reciprocating movement not only in the direction of its axis, but in a direction perpendicular to this axis, thus ensuring a scanning in a perpendicular direction.

In the embodiments of Figs. 6 and 7, the wave guide is provided with dielectric elements I for radiating electromagnetic waves and said rotating means are operated to ensure the desired scanning.

In the modification of Fig. 6, the radiating ele ments 1S are xed with respect to wave guide 2 on one face thereof and the opposed face of said guide is provided with rods Il slidable therein and subjected to the action of cams l2 cooperating with suitable springs to control the depth of engagement of rods Il in the wave guide.

The periodical law of displacements of said rods l l with respect to guide 2 controls the variation of distribution of the neld and therefore the scanning of the electromagnetic beams.

In the modification of Fig. 7, radiating elements l@ are pivotally mounted with respect to guide 2 and they are oscillable simultaneously by means of a rod I3.

With any of these arrangements we obtain a at wave beam the approximate shape of which is shown by Figs. 8a (projection on the plane to which all parabolas P1 are parallel) and 8b (projection on a plane parallel to that of parabola P2), this ilat beam rotating about an axis located in the plane of Fig. 8b so as to scan an angle represented by double arrow F (Fig. 8a)

In a general manner, while we have, in the above description, disclosed what we deem to be practical and eicient embodiments of our invention, it should be well understood that we do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What we claim is:

1. In combination, a fixed wave guide of the hollow type, provided with a plurality of slots in its wall, said slots being positioned to ensure directional radiation of electromagnetic waves and means for periodically displacing the whole of said slots in a direction parallel to said wall physically relative to said wave guide.

2. An antenna according to claim 1 in which said wave guide includes a xed portion consisting of a prismatic box having three solid walls forming three faces of a rectangular prism and open along the fourth face of said prism, and a strip movable longitudinally along said fourth face, said strip forming the fourth wall of the wave guide and bein-g provided with longitudinal slots in line with one another, the means for periodically displacing said slots including two drums disposed on either side of the ends of said box and about which said strip is wound in an endless manner.

3. An antenna according to claim 1 in which said wave guide includes a fixed portion consisting of a prismatic box having three solid walls forming three faces of a rectangular prism and open along the fourth face of said prism, and a strip movable longitudinally along said fourth face, said strip forming the fourth wall of the wave guide and being provided with longitudinal slots in line with one another, the means for periodically displacing said slots consisting of means for periodically displacing said strip along said open face of said box.

THO KAHAN.

ALBERT Waarin'.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,075,808 Fliess Apr. 6, 1937 2,409,183 Beck Oct. 15, 1946 2,434,253 Beck Jan. 13, 1948 2,436,380 Cutler Feb. 24, 1948 2,438,735 Alexanderson Mar. 30, 1948 2,453,414 De Vore Nov. 9, 1948 2,477,510 Chu July 25, 1949 2,482,162 Feldman Sept. 20, 1949 

